The dose of CVA21 for this study is 3 x 108 TCID50 (about 4.5 x 106 TCID50/kg for a 70-kg patient) by IT administration. Each patient will receive 4 separate CVA21 administrations in the first 8 days on trial (Days 1, 3, 5 and 8), followed by a fifth dose 2 weeks later (Day 22) and further administrations at 3 weekly intervals (Days 43, 64, 85, 106 and 127, up to a maximum of 10 sets of injections) or until confirmed disease progression or development of excessive toxicity.